Inductive railway train communication system



Oct. 14, 1952 A. J. SORENSEN 2,614,209

INDUCTIVE RAILWAY TRAIN COMMUNICATION SYSTEM Filed Nov. 29, 1947 2 SHEETSSHEET 1 will ('arA VJ IN V EN TOR.

Andr JiSorensen BY g HIS ATTORNEY Oct 14, 1952 A. J. SORENSEN 2,614,209

INDUCTIVE RAILWAY TRAIN COMMUNICATION SYSTEM Filed NOV. 29, 1947 2 $HEETSSHEET Z Fig: 3.

Wayside Sidlian 11.1. LIZ

Eq'uzjomem 012 (21F Equipment on Locomofive Fig. 4.

IN VEN TOR.

Andre J Sorensen HIS ATTORNEY Patented Oct. 14, 1952 INDUCTIVE RAILWAY TRAIN COMMUNI- CATION SYSTEM Andrew J. Sorensen, Edgewood, Pa., assignor to I Westinghouse Air Brake Company, a corporation of Pennsylvania Application November 29, 1947, Serial No. 788,945 t Q 6 Claims. (01. 246-8) My invention relates to inductive railway train communication systems and particularly to an inductive railway train .communication system utilizing portable units ior communicating between diiferent locations on a railway train and also for communicating between a railway passenger train and a wayside location;

It has heretofore been proposed to provide inductive railway train communication equipment which may be used for communication between the locomotive and caboose of freight trains, as well as communicating between these locations and the wayside locations. .Such equipment is usually permanently installed on the locomotive and caboose and is not readily portable. On passenger trains, usually only the locomotive is so equipped, and no inductive communication equipment is providedv on the passenger cars.

Accordingly, it is an object of myinvention to provide an inductive ltrai'n communication system incorporating one or more portable units which may be easily and quickly. installed on any car of a passenger train.

Another object of my inventionis to provide-an inductive train, communication system incorporating portable units which may bearranged to provide communicationbetween any two cars in,

the train, or between any car. in the train and the locomotive.

A further object of my invention is to provide an inductive train communication system utilizing permanently installed inductiye communication equipment on the locomotive: or, some other train caras a train-carriedrepeater station.

Other object-sci my invention and features of novelty will be apparent, from the following description taken in connection with the accom-v panying drawings. In practicing my invention, I provide a portable transmitter and receiver of the inductive type which is equipped with flexible leads having clamping means attached to the ends thereof to permit the leads to be clamped to the structure of a railway car. The points for attaching the leads are selected so'that a loop circuit including the track rails is formed, and which loop circuit is disposed for inductive relationship with a longitudinal circuit including line wires adjoining the tracks.

A similar arrangement of apparatus maybe provided on another car of the train, so that the energy induced in the wayside longitudinal circuit by the first transmitter and its associated loop circuit will be picked up by the loop circuit associated with the second equipment and actuate the receiver of the second equipment, and

vice versa.

Since the portable transmitter has a relatively low power output, the range of theequipment 5 "will be limited and in order to provide communication between. the portable equipment and a wayside location some. distance away, I provide means for employing inductivecommunication equipment permanently installed on the locomotive or some other car of. the: train as a traincarried repeater station whereby .thelow poweroutput of a portable transmitter having a preselected carrierfrequency.isretransmitted at a higher power level on a different irequency,

I shall describe certain: forms of railway train inductive. communication equipment embodying my invention and shall .then pointout the novel features thereof in claims} In the drawings,

'20 Fig. 1 is a-diagrammati view showing portable inductive communication equipment of a preferred embodiment of-,my invention when installed on a car of a passenger-train. r

Fig. 2 is a diagram showing the inductive rela -'tion of the equipment of Fig.- l with the wayside line wires and a second set of equipment. 1 i

Fig. 3 is a diagrammatic View showing one form of permanently installed inductive communication equipment locatedon a locomotivegand gg arranged to provide atrain-carried repeater'sta- Y tion for the portable equipment, and which repeater equipment also. embodies my invention.

Fig. 4 is-a diagram showingthe relation between the portable equipment located on acar of 52. passenger train, the locomotive, and a wayside station.

Similar reference characters refer to simila parts in each of the several views.

Referring to the drawings, Fig. l'shows-a-iragd mentary sectional view; of two passenger cars A' and B coupledtogether. The referencecharaoter 2 designates thevestibule space at the endfof each of the carsE-with al door-t openinginte the rnain compartment on the car, .Each of the cars 'is equipped with. a vestibulediaphragm, sothat when the cars are-coupled together, a flexible,- weatherproof passageway betweerrthe cars is I established. The vestibule diaphragms are shown as comprising a bellowsi usuallymade of rubber; rubberized canvas, -01, other flexible waterproof material. At the outermost end of the bellows 5, metal chafing plates 1 are attached to -form a bearing surface between the-diaphragrns, Buf-Z;

fer plates 8 areemployed -1to-;ho1'd the diaphragmsr 5. in their extended position by means of springs; I 1' not shown, and the buffer plates additionally provide a surface over which passengers may walk from one car to the other. The car couplings I operate in the usual manner to couple the cars together.

The portable communication equipment comprises a portable inductive transmitter and receiver I4 having a telephone hand set I8.

This portable transmitter-receiver unit I4 is shown conventionally since it may be any one of several different types and it may be of the type shown in an application for Letters Patent of the United States, Serial No. 756,363, filed June 23, 1947, by Adrian R. Doucette. The unit I4 may be provided with a carrying strap as shown in the Doucette application and the unit carried by an operator standing in the vestibule. It can be placed on the floor of the car or suspended from some part of the vestibule, and as illustrated the unit I4 is carried above the floor by some means not shown. The circuits and structure of the transmitter and receiver I4 are not shown since their specific arrangement forms no part of my present invention. It is sufiicient for this disclosure to point out that the transmitter and receiver are selectively connected to a pair of terminals I I and I3 through a press-totalk button for two-way communication. The transmitter when energized and connected to the terminals II and I3 is efiective to supply a carrier of a given frequency modulated by voice frequency which can be created by speaking into the microphone of the hand set I6 and the receiver when effectively connected to terminals I I and I3 is operative to demodulate carrier telephone energy applied to the terminals and reproduce the message in the ear phone of the hand set. The Doucette application shows an air core loop connected to terminals II and I3 for sending and receiving and while such equipment opcrates excellently when the air core loop is not shielded from the wayside line wires, it is obvious that the metal body of a railway car would shield the loop of such equipment located within the car in such manner as to effectively prevent the proper inductive relationship between the air core loop and the wayside line wires. The arrangement of apparatus embodying my invention obviates this difliculty by providing a loop circuit whichincludes the metal bodies of the cars, the wheels of adjacent coupled cars and the rails extending between the wheels of the adjacent trucks of the coupled cars and thereby provides in e fect and air core loop circuit which is'unshielded and disposed for inductive relationship with the wayside line wires paralleling the track. As shown in the drawings, two flexible wire leads LI and L2 are connected to the terminals I I and I3. re pecti e of the portable transmitter and receiver unit ll.

Each of the lead wires LI and L2 is provided with a clamping device I at its outermost end. and by means of the clamping device, the lead L2 is connected to the metal body of the car on the right at some convenient point, such as, for example, the hand hold or "grab iron I8, and the lead LI is connected to the metal body of the car on the left at some convenient point, such as, for example, the hand hold 20. A condenser 22 is shown connected in series with the lead LI, for purposes which will be subsequently explained. I

Several 100p circuits can betraced, each of which affords a complete circuit including the terminals II and I3 of the transmitter-receiver I4. For example, a circuit can be traced from terminal II, through condenser 22, lead wire LI, the hand hold 20 of car A on the left, the chafing plates I and the buffer plates 8 of the vestibule diaphragms between the cars, the hand hold I8 of the car B on the right, and lead L2 to terminal I3. Another circuit may be traced from terminal II of transmitter-receiver I4 through the condenser 22, lead wire LI, hand hold 23 and frame of the car on the left, through the joined couplers II] of the cars, the frame and hand hold N3 of the car on the right, and the lead L2 to the terminal I3. Another circuit may be traced from the terminal II of the transmitter-receiver l4 through condenser 22, lead wire LI and hand hold 20 of the car on the left, through the metal body of the car on the left to the truck bearing 24, the wheels and axle 26, the rails 28, the wheels and axle 26 of the car on the right, the truck bearing 24 of the car on the right, the metal body of the car to hand hold I8, and lead wire L2 to the terminal I3. It will be apparent that all of the paths traced above form parallel circuits each of which has a relatively large cross section. However, the circuit including the chafing plates I and buffer plates 8, and the circuit including the couplers I0, although shorter than the circuit including the wheels and the rails will be ordinarily of much higher resistance, since these parts are exposed to the weather and are usually covered by rust and dirt, as well as the fact that in the couplers I0 and the chafing plates 1 and buffer plates 8, the contact is of a sliding nature as the cars move along the track, so that the resistance of these circuits may be constantly changing.

It will be seen that the loop circuit having the least resistance'is that including the metal bodies of the cars, the trucks of the cars, the wheels and axles, and the stretch of rail 23 extending between the adjacent trucks of the coupled cars.

Since the frequency of the energy used in this communication system is relatively high, the loop circuit including the bodies of the cars and the rails has an appreciable amount of inductance. The condenser 22 is selected in a range so that it combines with the inductance of the loop circuit to form a series resonant circuit, thereby increasing the efliciency of the loop circuit, and matching the loop circuit to the output of the transmitter and to the input of the receiver of unit I 4. Although condenser 22 has been shown external to the transmitterreceiver I4, it is to be understood that in actual practice the condenser 22 would be mounted in a housing adjacent the transmitter-receiver I4, or mounted as an integral part of the portable unit.

From the foregoing, it will be seen that with the equipment arranged as shown in Fig. 1, there is formed a relatively large loop disposed in a vertical plane so that it has effective inductive relation with line wires paralleling the track occupied by the cars A and B. Thus high frequency energy supplied to the terminals II and I3 of the unit I4 is caused to circulate in the p circuit and creates a corresponding magnetic field that will link the parallel line wires to induce an electromotive force therein. Conversely, a magnetic field created of such high frequency energy flowing in the line wires threads this loop circuit and induces therein an electromotive force that is applied to terminals II and I3.

Referring to Fig. 2, there is shown a diagram which illustrates the manner in which the loop circuit previously described in connection with Fig. 1 is inductively coupled to a longitudinal circuit including line wires adjacent the track, and thus provides communication with another car on the train. As shown, in Fig. 2 the transmitter-receiver I4 located in car B is provided with a loop circuit which includes the truck of car B, the adjacent truck of car A, the rails 28 extending between the trucks, and the leads LI and L2. The high frequency energy flowing in this circuit causes an electromagnetic field to be set up as shown by the flux lines 30 and, which links the loop circuit of the equipment on cars A and B with the wayside line wires 32 which form a longitudinal circuit extending alon the track. Additionally there is shown cars C and D at some other location in the train, and which cars are equipped with an arrangement similar to that provided for cars A and B. Accordingly, it will be seen that the high frequency energy circulating in the loop at the location of cars A and B induces energy in the longitudinal line wire circuit comprising the line wires 32, and this energy travels along the longitudinal circuit and induces energy in the loop associated with the equipment provided for cars C and D, so that communication may be established between the two points of the train. For sending from the equipment on cars C and D to the equipment on cars A and B the action is reversed, the loop circuit on cars C and D serving as the sendin loop and the loop circuit on cars A and 13 serving to receive.

Since the transmitter-receiver I4 is of necessity a low power device, the energy supplied to the longitudinal circuit including the line wires 32 will be limited so that communication may only be established over a limited range when using the transmitter-receiver I4. I have found by experiment that the range of the equipment as shown is sufficient to cover the length of a relatively long passenger train, but is insufficient to communicate with wayside stations which are located an appreciable distance from the train.

Accordingly, I provide means for the retransmission of the communication supplied from a portable unit on a passenger car by a high-powered permanently-installed equipment preferably located on the locomotive of the train when communication is desired between the low power portable unit and a wayside station located at some distance from the train. Such permanently installed equipment would be preferably of the two-frequency-channel type and may be similar to that disclosed in an application for Letters Patent of the United States, Serial No. 575,311, filed January 30, 1945, by P. N. Bossart for Railway Train Communication Systems, now Patent No. 2,484,680, issued October 11, 1949, and to which application reference is made for a full understanding of two-frequency-channel inductive train communication equipment. It is sufficient for this application to point out that such equipment preferably includes two independent receivers and a transmitter. One receiver is adapted to pickup and demodulate a carrier communication current of a first or low channel frequency and the other receiver is adapted to pickup and demodulate a carrier communication current of a second or high channel frequency. The transmitter is adaptable of being conditioned to send communication current of either the low or the high carrier frequency.

As an aid in the understanding of my inven- 6 tion, I shall assume that the high and low frequency channels used by the permanent equipment are of 144 kc. and 80 kc., respectively, and that the portable equipment of Fig. 1 uses the high 144 kc. frequency. Referring to Fig. 3, a locomotive indicated conventionally at LO has permanently mounted thereon such two-frequency-channel inductive communication equipment. In Fig. 3 there is shown only that portion of the communication equipment necessary for a full understanding of my invention, the remaining portion being omitted for the sake of clarity.

As shown, a receiving coil RC mounted upon the locomotive for inductive relation to line wires is connected to the input terminals of a high frequency inductive communications receiver 36, the frequency of the receiver being the same as that of the transmitters and receiver 14 installed in the cars. The output of the high frequency receiver is supplied through the contacts 38 and 40 of a switch 5 in its normal position to a loud speaker LS located in the cab of the locomotive.

The transmitter of the permanently installed locomotive equipment is shown in block form at 42, this transmitter being adaptable of being conditioned to supply to an output transformer 0T communication current of either the high or the low channel frequency. A secondary winding of the output transformer OT is connected to a train carried loop illustrated at TL and which loop would be mounted on the locomotive in any suitable manner for inductive relationship with the line wires. The loop TL may be, for example, similar to that shown in Letters Patent of the United States No. 2,064,642, granted December 15, 1936, to P. N. Bossart for Railway Train Communication Systems. The transmitter 42 is provided with a selector switch SL for selecting the channel frequency, the arrangement being such that when the switch SL is set to the right to close a contact 50 a connection is completed for the transmitter to supply the high channel frequency when it is energized in a manner to shortly appear, and when the switch SL is set to the left closing contact 5| a connection is completed for transmitter 42 to supply the low channel frequency when it is energized.

When the locomotive equipment is being operated in its usual manner, the channel frequency of the transmitter 42 is modulated by means of a microphone MIC, and a push button PTB is provided to energize the transmitter in the wellknown push-to-talk arrangement. In addition I provide a contact 44 of switch S, which also serves to actuate the transmitter when the switch S is operated.

When the switch S is operated to its lowermost position, the contacts 38 and 4E! of the switch connect the output of the high frequency receiver 36 to the input of the transmitter 42, so that the output of the receiver modulates the transmitter. Additionally, when switch S is operated to its lowermost position contact 44 is closed to energize the transmitter 42.

In describing the operation of the train-carried repeater equipment of Fig. 3, I shall assume the locomotive LO on which the equipment of Fig. 3 is installed is attached to the train of which the cars A and B having the portable unit l4 carried thereon are a part. If the conductor of the train wishes to talk with the engineman, the conductor would operate the unit [4 and by talking into the microphone of the hand set It, the modulated telephone current of the high 144 kc. channel frequency is supplied to the wayside longitudinal circuit in the manner previously described. This energy is picked up by the receiving coil RC on the locomotive and applied to the receiver 35, where it is amplified and demodulated and then supplied to the loudspeaker LS. If the engineman wishes to reply to the conductor, the engineman sets his selector switch SL to the right and then by pushing the push button PTB and speaking into microphone MIC the modulated energy of the 144 kc. frequency is supplied through loop TL to the longitudinal line circuit. This line circuit energy is picked up by the loop circuit at the unit 14 and applied to its receiver where it is demodulated and supplied to the earphone of the hand set I6. Thus the conductor and engineman can carry on a two-way conversation.

I shall next assume that the conductor of the train wishes to talk with an operator in a wayside station which is some distance from the train and beyond the range of the unit 14. The conductor would first call the engineman in the manner previously explained and instruct him to set his equipment to function as a repeater. To do this the engineman would set his selector switch SL to the left to condition the transmitter 42 for operation on the low 80 kc. frequency, and then would operate the switch S to its lowermost position. When this is done the transmitter 42 is made active through the closing of contact as of switch S, and the audio frequency output of receiver 36 is supplied to the input of transmitter 42 through contacts 33 and d of switch S to modulate the 80 kc. channel frequency, and the output of the transmitter 42 is supplied to the longitudinal line circuit through the loop TL.

Thus the communication energy on the 144- kc. channel frequency sent out from the portable unit M on the car A is received at receiver 35 on the locomotive and the intelligence is retransmitted by the locomotive transmitter 42 on the low 30 lzc. channel frequency and at a high power level. This high power level energy is then transmitted to the wayside station with which the conductor wishes to talk through the longitudinal line circuit, assuming the wayside station is within the transmission range of the permanently installed communication system.

Gne such way in which a conversation may be carried out from the equipment on the car with a wayside station is illustrated in Fig. 4. Referring to Fig. 4 the equipment on the car transmits at high frequency to the equipment on the locomotive as shown by the arrow M, and the equipment on the locomotive receives the intelligence on the high frequency carrier, and retransmits it on a low frequency carrier on a higher power level to the wayside station through the longitudinal line circuit as indicated by the arrow 46. The wayside station may then reply to the equipment on the car by transmitting at a high power level with ahigh carrier frequency directly to the equipment on the car through the wayside longitudinal circuit as shown by the arrow 48.

From the foregoing, it will be seen that my invention provides for an inductive train communication system which is readily portable and may be installed on any car of a passenger train, to provide communication between that car and another car on the passenger train, or between that car and the locomotive of the train, or between the car and a wayside station with the aid of atrain-carried repeater which utilizes the permanently installed inductive train communication equipment located on the locomotive with only a minimum change in the circuits and operation of the equipment installed on the locomotive.

Although I have herein shown and described only certain forms of railway train inductive communication equipment, it is to be understood that various changes and modifications may be made therein within the scope of the appended claims without departing from the spirit and scope of my invention.

Having thus described my invention, what I claim is:

1. The method of communicating between a car of a passenger train and a wayside station when the train is more than a predetermined distance from the station, comprising the steps of transmitting from said car communication energy on a first carrier frequency and at a relatively low power level incapable of providing communication between said car and said station, inductively receiving the communication energy on a locomotive of the train, retransmitting the intelligence of the communication energy on a second carrier frequency and at a relatively high power level, inductively receiving the retransmitted communication energy at said station, replying at said station on said first carrier frequency and at a relatively high power level, and inductively receiving the reply communication energy at said car.

2. In combination with a first and a second railway car coupled together, said cars having metallic bodies, an inductive train communication system comprising a portable inductive transmitter and receiver unit equipped with a pair of output-input terminals, and a loop circuit for said transmitter and receiver formed by electrically connecting one of said terminals to the metallic body of said first railway car at a first point, and connecting the other of said terminals to the metallic body of said second car at a second point, said points on said first and second cars being selected to form a loop circuit of relatively large area and including a metallic path between said coupled cars of relatively low resistance with respect to other metallic paths between said points on the bodies of said coupled cars.

3. A loop circuit for an inductive train communication system formed by establishing electrical connections to the metallic bodies of two coupled railway cars at points on the bodies of the cars selected to provide a loop circuit of relatively large area and having a relatively low resistance with respect to other metallic paths between said points on the bodies of. said coupled cars.

4. In an inductive railway train communication system for passenger trains, the cars of which have metallic bodies, the combination comprising an inductive transmitter and receiver having a pair of terminals to which the transmitter and receiver are selectively connected, said transmitter and receiver being located in a first passenger car and having one terminal connected to the metal body of the car at a first point, a second passenger car coupled to said first passenger car, and means for connecting a second terminal of said transmitter and receiver to the metal body of said second car at a second point, said points being selected so that a loop a low resistance with respect to other metallic paths connecting the bodies of the coupled cars.

5. In an inductive railway train communication system, the combination comprising two coupled cars having metal bodies, a portable transmitter-receiver unit having two terminals to which the transmitter and receiver are selectively coupled, a lead wire for each of said terminals, and a loop circuit formed by connecting one of said wires to the metal body of one of said cars at a first point, and connecting the other of said wires to the metal body of the other car at a second point, said points being selected so that a loop circuit is formed by the said lead wires, the metal bodies of the cars, the adjacent pairs of wheels of said cars, and the track rails between the adjacent pairs of wheels of said cars, and has a low resistance compared to other metallic paths between the coupled cars, whereby a loop of relatively large area and low resistance is obtained.

6. In a railway train communication system for providing two-Way communication between two spaced points on a train and between each of said points and a wayside station when the I a modulated carrier of a first or a second carrier frequency and a selector to select the carrier frequency which is to be supplied, the receiver including demodulating means effective to reproduce the modulating frequency of either said first or second modulated carrier, said equipment of said one point having a transmitter including modulating and generating means operable to supply a modulated carrier of said first carrier frequency and having a receiver including demodulating means effective to reproduce the modulating frequency of said first modulated carrier, and manually operable switching means at said other train point to connect at times the output of its receiver to the input of its transmitter, whereby modulated carrier of said first frequency transmitted at said one train point is received at said other train point and retransmitted as modulated carrier of said second frequency and. modulated carrier of said first frequency transmitted from said wayside station is received at both said train points.

ANDREW J. SORENSEN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,008,280 Hopkins July 16, 1935 2,090,492 Udstad Aug. 1'7, 1937 2,112,364 Grondahl Mar. 29, 1938 2,327,249 Cravath Aug. 17, 1943 2,407,417 Halstead Sept. 10, 1946 

